The present invention encompasses an apparatus and method for minimizing or eliminating light streaks that appear in yarns tufted into a carpet, in which the undesired light streaks result from the yarn being overly crimped in a stuffer box after a shutdown of the production line. By decreasing the quantity and length of light streaks, the present invention reduces the amount of unacceptable carpet formed, which increases efficiency and saves carpet producers money.
As an overview, a large portion of carpets used in residences are known as pile carpets formed by tufting pile yarn into a primary backing material. The yarns tufted into the primary backing form the fibrous face of the carpet. The tufted loops can optionally be cut or sheared to form tufts of a desired, constant vertical height.
Two general categories of tufted carpets are (1) a textured style, in which the tufts and the individual filaments or staples have varying degrees of crimp or curl; and (2) a straight-set style, in which the filaments or staples at the tuft tip are straight and substantially perpendicular to the plane of the carpet face. Addressing the first category of carpets, yarn that is used as pile in textured style carpets is prepared by cabling together a plurality of single yarns and setting them in their twisted condition. One option is to use a stuffer box, or stuffer box crimper, to produce textured yarn having a desirable appearance and texture when tufted into the primary backing. The purpose of the stuffer box is to put texture in the twisted yarn. One major stuffer box brand uses the tradename Superba(copyright).
During operation of such a stuffer box, uncrimped yarn is transported by a pair of counter-rotating nip rolls into and through a confined zone within the interior of the stuffer box. There, the yarn is caused to be folded and compressed into a fine crimp configuration. The crimps in the yarn can then be heat set, which xe2x80x9clocks inxe2x80x9d or sets the texture to make it of a lasting nature. The more the yarns are textured, the lighter the color because more light is reflected from the crimps and elbows formed into the yarns.
The latter type of carpet, the straight-set style, does not use a stuffer box in the production line. As such, the filaments or staples at the tuft tip are straight and substantially perpendicular to the plane of the carpet face. Without processing the yarns through a stuffer box and texturing the yarns prior to tufting into the primary backing, the untextured carpet has a darker appearance than if the same carpet was formed by the identical yarn strands processed in a stuffer box and then heat set.
The textured-style carpets are more popular than the straight-style carpet because, for example, the texturing characteristics assist in hiding footprints and vacuum tracks. The step of texturing the yarns with the stuffer box, however, creates some issues that do not exist when producing the straight-style carpet. One such recurring problem arises after a shutdown of the heat-set production line, which occurs periodically for doffing the winders, other planned line stops, and aberrant conditions that may arise during operations. Once operations resume, some of the yarns have a lighter appearance than yarns processed during normal operating conditions, i.e., before and after the shutdown.
It has been found that the yarns remaining within the stuffer box during and through the shutdown result in the lighter colors. This yarn obtains too much texture by remaining in the stuffer box longer than the normal processing time. The lighter appearance of the overly textured yarns is particularly apparent when they are tufted into the primary backing and appear as light streaks in fiberous face of the tufted carpets. This lighter section of the tufted carpetxe2x80x94located between yarns processed by the stuffer box during normal operationsxe2x80x94is unacceptable from a quality-control standpoint and are not marketable.
The present invention addresses this problem in the art and eliminates or minimizes the amount of carpet that must be wasted as a result of overly texturing the yarn during a shutdown. More specifically, the present invention comprises an apparatus and method that involves opening the outlet of the stuffer box, immediately after shutdown and also injecting one or more bursts of a fluid, preferably air, into the stuffer box. The fluid passes through a portion of the stuffer box and out of the opened outlet, entraining some of the yarns remaining within the stuffer box after the shutdown. Some of these entrained yarns pass through the outlet to exit the interior of the stuffer box, where they remain permanently.
The portion of the yarns moved to outside of the stuffer box by the air (referred to as the first portion of the yarns) is thus not overly crimped because the yarns are free to expand unimpeded by the interior walls of the stuffer box. In conjunction, the portion of the yarns remaining within the stuffer box after the first portion of the yarns is blown out (referred to as the second portion of the yarns) has an increased volume to expand. Thus, the present invention reduces the degree of crimping of both the first and second portions of the yarns since the first portion that is blown out is free to expand and the second portion that remains within the stuffer box has more volume into which it may expand after the first portion is blown out.
Accordingly, by using the present invention, the yarn located within and removed from the stuffer box at and after the time of shutdown maintains a texture closer to that of the yarns processed in the stuffer box during normal operations. Any light steaks that do exist when the manufacturing operations resume are shorter in length compared to not using the present invention. That is, the longitudinal or warp length of the tufted carpet that is unacceptable is reduced in size using the present invention compared to using previous industry practices of leaving all portions of the yarn within the stuffer box during a shutdown. Thus, compared to the prior art practices, the present invention reduces waste by eliminating or minimizing the quantity of unacceptable carpet that exists after a shutdown of the production line.
Without using the present invention, in contrast, none of the yarns remaining within the interior of the stuffer box after shutdown will be removed during the period of the shutdown and thus will be subject to greater pressures from the adjacent yarns. These greater pressures increase the number of elbows and result in more texture in the yarn. As noted above, compared to other yarns processed by the stuffer box during normal operations, the more textured yarn reflects more light and thus appears as a discoloration in the carpet, resulting in an unacceptable product that cannot be sold to consumers.